7-Dehydrocholesterol: Cholesterol Precursor, Previtamin, and Smith-Lemli-Opitz Biomarker

Posted on June 21, 2022


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You may have never heard of 7-dehydrocholesterol (7-DHC) but that doesn’t mean that it’s not important! Not only is 7-DHC an important precursor to cholesterol, but it is also necessary to produce vitamin D3 in your skin. 7-DHC enables your skin to manufacture vitamin D3 from ultraviolet B (UV-B) rays from sun light – so, 7-DHC is also considered a provitamin of vitamin D3.

7-Dehydrocholesterol

7-DHC, as well as cholesterol, are biomarkers of a developmental disorder called Smith-Lemli-Opitz syndrome (SLOS). 7-DHC is elevated in SLOS (about ten times higher than in healthy individuals). It shouldn’t come as a surprise then to learn that cholesterol levels are extremely low in SLOS individuals since 7-DHC is a precursor of cholesterol. SLOS syndrome affects many parts of the body and is characterized by distinct facial features, microcephaly, intellectual disability, and behavioral issues. This syndrome only affects about 0.0025% of newborns but that’s really more common than you might think. 0.0025% of newborns means that 1 out of roughly 40,000 suffer from Smith-Lemli-Opitz syndrome.

Diagnosis, treatment, and intervention of SLOS can greatly improve the condition of newborns, so it is important to have effective diagnostic methods in place to detect SLOS.

Even with the knowledge that high 7-DHC and low cholesterol were characteristics of SLOS, a simple, effective diagnostic method for the detection of 7-DHC was not discovered until this year. Researchers from Shanghai sought to develop a reliable, simple diagnostic method for simultaneously determining levels of 7-DHC and cholesterol in human hair.

The method described in this research follows strict protocols and involves the following steps:

  • Decontamination – guidelines set by the Society of Hair Testing were followed.
  • Amount of Hair Sample – the amount of hair taken as a sample was 10 mg. The sample was then digested in an alkaline medium and 1/10 of the total volume was used for final analysis (1 mg of hair).
  • Homogenization – 1-2mm hair pulverized by Bead Ruptor was chosen as the best homogenization method.
  • Extraction of 7-DHC and cholesterol from hair – the optimal extraction conditions were mixed diameter ceramic beads at -30°C with a single program run.
  • Antioxidants – Due to the oxidizable nature of 7-DHC, and to a lesser extent cholesterol, an antioxidant was used to protect them from oxidation.
  • Liquid-liquid extraction method – the optimal method was found to be a single extraction using 900 µL of n-hexanes.

The method was then validated by using a developed stripped matrix strategy. The range was wider than published methods and covered the reported levels of both compounds and thus met standards set forth by the FDA and EMA.

This method was then applied to samples taken from healthy and SLOS affected individuals. The number of SLOS affected patients from which samples were taken was small. But the results clearly showed a difference in levels of 7-DHC and cholesterol between the healthy and SLOS patients. This diagnostic method still needs to be extended to a larger number of patients to establish cut-off values for SLOS diagnosis using human hair.

This research still has a long way to go before it can be used as a diagnostic method in a medical laboratory setting, but it is a large step towards the development of a powerful diagnostic tool for SLOS.

METLIN’s CCS database of more than 860,000 lipids already includes 7-DHC, so if you want to see MS/MS and ion mobility data for 7-DHC, head over to METLIN and take a look! Click HERE to purchase 7-DHC for your own research!

Enjoy the full research article at the following link! https://www.jlr.org/article/S0022-2275(22)00061-X/fulltext